BOM removal during biological treatment: A first-order model

Using data from two pilot-scale studies and one full-scale investigation, this article demonstrates that the removal rate in biological water treatment is proportional to the influence concentration to the bioreactor, i.e., a first-order process. This is true not only for measures of biodegradable organic matter, e.g., assimilable organic carbon, but also for precursors of chlorination by-products such as trihalomethanes. The slope of the removal rate versus the influent concentration relationship is termed the average specific removal rate, r[sub AS]. When data were available from different studies, the r[sub AS] values tended to fall in the same range. With a first-order model, the performance of biological treatment in a given situation can be estimated from limited data. The model is suggested as an approach for the preliminary design of bioreactors for drinking water treatment.